1. Field of the Invention
The present invention relates to the decatizing of fabrics.
2. Description of the Prior Art
There is disclosed in my U.S. Pat. No. 3,885,262 a method of, and apparatus for, continuously decatizing woven fabrics, knitted fabrics and other fabrics, using at least one steam cylinder and one suction cylinder, over each of which a respective endless pre-tensioned backing cloth is guided and which presses the fabric against the associated cylinder, the tensions in the parts of the backing cloths extending around the cylinders being variable independently of one another.
This method and apparatus provide good decatizing effects and also useful shrinking effects.
With certain fabrics it is preferred to provide only a relatively low surface pressure during steaming, and a relatively high surface pressure during the suction treatment. However, with other fabrics it has been found more advantageous to make the surface pressure during steaming substantially higher than during the suction treatment. To obtain the required surface pressure, the backing cloths are used as pressure bands and, by being tensioned in the longitudinal direction, exert a radial pressure on the fabric in the region of the respective cylinder, independent of the pressure at the other cylinder.
It has been found that when the surface pressure is significantly increased a better and more noticeable decatizing effect can be produced. It has also been found that the intensity of the decatizing effect is primarily dependent on the magnitude of the surface pressure during the treatment.
However, there are limits to the possible increase of these decatizing effects. With the method and apparatus disclosed in the aforesaid U.S. patent, conventional finishdecatizing effects and also slight lustre decatizing effects can be achieved without difficulty. But if it is desired to increase the effect further to provide lustre decatizing and boiler decatizing, difficulties do arise.
These difficulties arise due to the fact that with high surface pressures, for instance above 0.4 kg/cm.sup.2, the surface of the backing cloth acting as a pressure ban tends to mark the decatized material, and also, since the tension required to produce surface pressures of this magnitude is relatively high, the backing cloth must consist of a very strong material. Since a certain air-permeability is also required, a relatively non-uniform surface structure is formed and irregularities on the surface and differences in smoothness and density cause the fabric to be marked during decatizing.